Date | November 2016 | Marks available | 5 | Reference code | 16N.2.SL.TZ0.2 |
Level | Standard level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
Command term | Explain and State | Question number | 2 | Adapted from | N/A |
Question
The image is an electron micrograph.
Determine, with a reason, whether the image is of a prokaryotic cell or eukaryotic cell.
(i) State the process that divides one nucleus into two genetically identical nuclei.
(ii) Explain how the cell cycle is controlled.
Markscheme
eukaryotic because nucleus/membrane-bound organelles/named organelle other than ribosome «eg, mitochondria, vesicles» internal membranes «ER»/multicellular
(i) mitosis
(ii)
a. cell cycle is a sequence of stages / cell cycle is G1, S, G2 and mitosis
b. (control of the cell cycle) by cyclins/cyclin
c. levels of cyclins rise (and fall)/fluctuate during the cell cycle/surge at different times/have to reach a certain concentration
d. conditions inside as well as outside the cell affect regulation
e. four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclins regulate the sequence/timing of the cell cycle / cyclins trigger the next stages
The idea of different cyclins acting at different phases must be clear.
f. cyclin-dependent kinases / cyclins bind to kinases and activate them
g. kinases phosphorylate other proteins
h. phosphorylated proteins perform specific functions in the cell cycle